将核心数据堆栈更新为applicationWillEnterForeground

Question

我和App groups在两个应用程序之间共享了相同的App groups。

当我在应用程序A中添加录音并打开App (第一次启动)时，App将正确检索数据。

当我在应用程序A和应用程序B中添加记录时(已经在后台启动)，我希望同步数据，当应用程序B返回到前台时，它可以检索数据。

这就是为什么当应用程序B回到前台时，我将核心数据袋更新为applicationWillEnterForeground。哪条路是对的？

let directory = NSFileManager.defaultManager().containerURLForSecurityApplicationGroupIdentifier("group.com.sl.sharedData");

        let url = directory?.URLByAppendingPathComponent("sharedData.sqlite")
        let store = self.persistentStoreCoordinator?.persistentStoreForURL(url!)
        var error : NSError?
        if false == self.persistentStoreCoordinator?.removePersistentStore(store!, error: &error)
        {
            println("error = \(error!.localizedDescription)")
            return
        }
        let options = [
            NSMigratePersistentStoresAutomaticallyOption: true,
            NSInferMappingModelAutomaticallyOption: true,
            // Adding the journalling mode recommended by apple
            NSSQLitePragmasOption: ["journal_mode": "DELETE"]
        ]
        var failureReason = "There was an error creating or loading the application's saved data."
        if self.persistentStoreCoordinator?.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: options, error: &error) == nil {
            // Report any error we got.
            var dict = [String: AnyObject]()
            dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data"
            dict[NSLocalizedFailureReasonErrorKey] = failureReason
            dict[NSUnderlyingErrorKey] = error
            error = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
            // Replace this with code to handle the error appropriately.
            // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
            NSLog("Unresolved error \(error), \(error!.userInfo)")
            abort()
        }
        _persistentStoreCoordinator = nil
        _managedObjectContext = nil
        let rootViewController = self.window!.rootViewController as ViewController
        rootViewController.context = self.managedObjectContext

不幸的是，它不像我想的那样起作用了。每次输入applicationWillEnterForeground时都会对检索到的数据进行配音。哪条路是对的？

//编辑2014/04/17 :尝试使用芒迪的解决方案

我和NSManagedObjectContextObjectsDidChangeNotification试过了

   func applicationWillEnterForeground(application: UIApplication) {

        NSNotificationCenter.defaultCenter().addObserver(
            self,
            selector: "mergeContextChangesForNotification:",
            name: NSManagedObjectContextObjectsDidChangeNotification,
            object: managedObjectContext)

        let rootViewController = self.window!.rootViewController as ViewController
        rootViewController.context = managedObjectContext
        }
    }

func mergeContextChangesForNotification(notification : NSNotification){
        let otherContext: NSManagedObjectContext = notification.object as NSManagedObjectContext

        if((otherContext != managedObjectContext) && (otherContext.persistentStoreCoordinator == managedObjectContext.persistentStoreCoordinator)){

            managedObjectContext.performBlockAndWait{ () -> Void in

                self.managedObjectContext.mergeChangesFromContextDidSaveNotification(notification)
            }
        }
    }

mergeContextChangesForNotification已被调用，但我从未在以下条件下输入：if otherContext != managedObjectContext) && (otherContext.persistentStoreCoordinator == managedObjectContext.persistentStoreCoordinator

Answer 1

如果应用程序已经处于活动状态，则不应该再次设置持久存储协调器。Xcode模板中使用的标准延迟初始化是足够和更好的。

相反，您可能需要侦听NSManagedObjectContextObjectsDidChangeNotification并酌情更新您的UI。